1. Field of the Invention
The present invention relates to a magnetron plasma processing apparatus used in, e.g., a semiconductor manufacturing system.
2. Description of the Related Art
As a conventional magnetron plasma processing apparatus, a dry etching apparatus and a thin-film deposition apparatus used in, e.g., the manufacture of semiconductor elements are known. In the magnetron plasma processing apparatus of this type, a plasma is generated in the processing chamber of the apparatus, and the function of ions, radicals, electrons, or the like in the plasma is utilized to perform desired processing (etching or thin-film deposition).
Such a magnetron plasma processing apparatus will be described by way of a magnetron plasma etching apparatus.
A magnetron plasma etching apparatus can perform evacuation and has a process chamber to which an etching gas can be supplied. A susceptor electrode for placing a wafer as an object to be processed and an upper electrode are provided in the processing chamber. Both the susceptor and upper electrodes are made of a conductive material. The upper electrode is grounded, and the susceptor electrode is connected to an RF power supply that outputs a high frequency power having a frequency of, e.g., 380 kHz or 13.75 MHz. With this arrangement, the upper and susceptor electrodes can be used as parallel plate electrodes to generate a plasma toward the wafer in accordance with cathode coupling (RIE). The ions or neutrons in the plasma react with or physically act on a silicon compound constituting the wafer, thereby etching the wafer.
In this apparatus, two permanent magnets supported by yokes are rotated by rotating shafts to generate between the upper and susceptor electrodes a magnetic field having a component parallel with the upper and susceptor electrodes. This aims at causing, by the function of the electric field generated between the upper and susceptor electrodes and the function of the component of the magnetic field perpendicular to the electric field, an electronic cycloidal movement in a direction perpendicular to both the electric field and the magnetic field to increase the frequency of collision between electrons and gas molecules. This increases an amount of generated plasma, and hence the etching rate.
In the plasma etching apparatus, the etching amount must be uniform throughout the surface of the wafer.
When, however, etching is performed by using the conventional magnetron plasma etching apparatus as described above, the etching rate generally becomes higher in the central portion of the wafer than in its peripheral portion, and thus the etching uniformity is not sufficiently satisfactory.
According to the studies made by the present inventor, in the central portion of a wafer, the magnetic field obtained by the permanent magnet is substantially parallel with the surface of the wafer, and thus the component of the magnetic field perpendicular to the electric field is strong. In contrast to this, the electric field generated in the peripheral portion of the wafer is not parallel with the surface of the wafer. Therefore, the component of the magnetic field perpendicular to the electric field is weak at the peripheral portion of the wafer, which is assumed to be the reason why the electronic cycloidal movement is unlikely to occur.
This problem happens not only in the magnetron plasma etching apparatus but also in a plasma sputtering apparatus or a plasma CVD apparatus which performs processing by using a plasma.